External validation of a simple risk score based on the ASPRE trial algorithm for preterm preeclampsia considering maternal characteristics in nulliparous pregnant women: a multicentric retrospective cohort study.
To validate the performance of a first-trimester simple risk score based on the ASPRE trial algorithm for pre-eclampsia.Multicentric retrospective cohort analysis.Four Italian hospitals.Unselected nulliparous women at 11-13 weeks gestation from January 2014 through January 2018.Model performance was evaluated based on discrimination and calibration.Delivery before 37 weeks gestation with a diagnosis of pre-eclampsia.Based on 73 preterm pre-eclampsia cases, and 7,546 controls (including 101 cases of late pre-eclampsia) , the area under the ROC curve was 0.659 (95% CI 0.579-0.726). The sensitivity was 32.9% (95% CI 22.1-43.7) at a false positive rate of 8.8%. The LR+ was 3.74 (95% CI 2.67-5.23), the PPV was 3.49% (95% CI 2.12-4.86%) and the NPV 99.3% (99.1-99.5%). The sensitivity and LR+ were approximately 40% lower than in the original study. The calibration analysis showed a good agreement between observed and expected risks (p=0.037). Comparison with the Fetal Medicine Foundation (FMF) algorithm yielded a difference in the Area Under the Curve (AUC) of 0.084 (p =0.007).In our Italian population, the simple risk score had a lower performance than expected for the prediction of preterm pre-eclampsia in nulliparous women. The FMF algorithm applied to the same data set resulted in a better prediction.